As human civilization advanced in Korea, an agricultural society gradually emerged. Ancient Koreans, who had originally lived around Mt. Bektu (between the borders of modern day North Korea and Manchuria), began to migrate southward and settle where the living environment was more attractive. Because of an increased awareness of and a greater fondness for territorial possession, it may be assumed that it was necessary to cultivate new and improved types of combative skills. A sedentary lifestyle led to a collective social body. In the communal system, clan units merged together into tribal units with clear distinction between the leaders and the followers. Feuds and struggles with other tribal units naturally resulted. Under these conditions, each clan would surely try to be mightier than other clans. To attain and maintain superior strength, people trained through running, wrestling, swimming, hand-to-hand fighting, and other such activities. It is natural to assume that the development of such weapons as staff, spear, swords, bow, and ax took place around this time.
The Gojoseon people gradually extended their influence not only over other tribes in the vicinity, but also to the north, conquering most of the Liaodong Basin. However, the rising power of the feudal state of Yen in northern China (1122-225 BC) not only checked Gojoseon's growth, but eventually pushed it back to the territory south of the Ch'ongch'on River, located midway between the Yalu and Taedong rivers, and took over the territory vacated by Gojoseon. The Chinese had discovered iron by this time and used it extensively in farming and warfare. The introduction of iron brought a variety of changes to Korea; iron hoes, plowshares, and sickles increased the ability for food production, thus, the gap between the ruling class, who monopolized the new sophisticated tools, and the poor increased.
The new name for the Korean Yen state was Wiman Choson. This confederated kingdom was grounded on the former Gojoseon power structure. The Yen ruler maintained some of the political, economic, and cultural features of the Gojoseon, keeping many of the high officials in place.